A prospective study to assess the clinical impact of interobserver reliability of sonographic measurements of fetal nuchal translucency and crown-rump length on combined first-trimester screening

OBJECTIVE To examine the interobserver variability for fetal biometric parameters and to focus on how this variability affects the combined first-trimester screening test results. METHODS Sixty-four singleton pregnancies who were scheduled for combined first-trimester screening were investigated. Two experienced sonographers performed all examinations at the same visit. The risk calculations of screening were performed according to the each operator's individual ultrasonographic fetal measurements. Interobserver variability in measurements of fetal nuchal translucency (NT) and crown-rump length (CRL) and the effect of this interobserver variability on the screening results were assessed. RESULTS Interobserver reliabilities for NT and CRL were 0.687 and 0.945 (p<0.001), respectively. Interobserver reliability coefficients for trisomy 21 and trisomy 13/18 were 0.945 and 0.963 (p<0.001), respectively. CONCLUSION Our study demonstrated quite high interobserver reliability for CRL measurement, while interobserver agreement for NT was lower. Despite this lower reliability and agreement for NT measurement, interobserver reliability for chromosomal abnormalities was quite high.